Molecular characterization of organic matter in B and C horizons of an acid forest soil

Abstract

Organic matter in B and C horizons of mineral soils is extremely important in terms of carbon sequestration of soils because it may contain stabilized carbon compounds. The aim of this study was to examine the composition of the organic matter found in deeper soil horizons and to compare it with the surface soil horizon. The conceptual approach included the analyses of bulk soil and particle size fractions by elemental analyses and isotopic characterization. The chemical structure of the organic matter was examined by 13C CPMAS NMR spectroscopy and pyrolysis GC/MS. Additionally single plant litter compounds were analyzed. Isotopic analyses pointed to an increasing degree of organic matter stabilization with depth. The chemical composition of the organic matter of the B horizons suggest that root-derived compounds are stabilized preferentially. In the C horizons, microbial compounds seem to dominate.